Commit

A Git commit is an immutable snapshot plus metadata: parent commit IDs, author, committer, message, and a tree object pointing at file blobs. Commits form a directed acyclic graph — each commit knows its parent(s), not the other way around.

					git add src/auth.ts
git commit -m "fix(auth): reject expired refresh tokens"
				

Good commits represent one logical change that can be reviewed, reverted, cherry-picked, and explained months later. Staging (`git add -p`) lets you split mixed working-tree edits into separate commits.

On interviews: explain commit identity (SHA-1 hash of content), why small commits help review and bisect, and how history supports release traceability.

Common pitfalls: huge mixed commits that hide rollback targets; rewriting public commits without coordination; committing secrets or generated artifacts that belong in `.gitignore`.

The trade-off is granular history (more commits) versus review noise — the unit should be logical, not microscopic.

Checklist:

• Explain commit identity and parent links.
• Keep one logical change per commit.
• Separate formatting churn from behavior changes.
• Stage deliberately with patch mode when needed.